heater control

[scott]

i'm new here, and i've got a problem that i cant figure out.  i own a 1985 c-10 that i've done a small amount of work on.  the previous owner had the stock 305 replaced with a goodwrench 350.  after i blew the 700r4 i replaced it with a turbo 400, and since the exhaust was in the way of the tranny swap, i hacked it off.......AND since i cut the exhaust off, i figured i'd replace the stock exhaust manifolds with some headers, and since i put some headers on i fugured i might as well............okay so i'm sure you can all see where this is going.......in any event, while i was changing the manifold/carburetor/ and the distributer.......my brother pretty much tore all the vacuum lines out of the old quadrajet.  now the problem is the heater controls........the heat works fine, but i cant get it to change from blowing heat out of the bottom ducts to say, defrost, or vent.  it ONLY blows out the bottom.......anyone know how to fix this?

thanks
scott

[84 silverado]

Scott, on the passenger side of your firewall there should be a small(probably 5/16 or so) vacuum line coming out of the wall between the evap case(inboard side) and the center of the wall. This hose runs to your hvac selector switch inside the truck. With no vacuum to it you'll never get the heater to change modes. Once you find the hose, connect it to the vacuum source you used for the modulator on your trans. It's usually the one that comes off the big port on the intake between the carb and distributor. This should have a multi-point connector on it because it's used for several different things. Hope this helps a bit and isn't too confusing. It's been a long day so I'm not sure how coherent I am!!!! Good luck, Bill

[scott]

Bill, thanks, i'm going to give it a shot......i'll let you know how i make out

scott

[87 deluxe]

I have similar problem exept I can obtain defrost but will not heat up inside. not through any vent. what do u suppose it is? thank you

[84 silverado]

Deluxe, you say you have defrost but no heat. Do you mean no warm air, or no mode control from vent to floor, etc, etc? If you have no directional control it's either a vacuum or controller problem. If you have no heat or temp change it's another problem with the temp doors in the heater box or a bad core. Also, the controls for an A/C truck differ from a non-A/C type. Be a bit more descriptive of you can and I'll try to steer you the right way or one of the other guys can give you a shot too. Good luck, Bill

[87 deluxe]

sorry guys:
I meant to tell you that the air that the heater blows out does not come out hot at all.
I can defrost the my windshield somehow but the air is not hot at all.
Can you please tell me whats going on?
thanks in advance and marry christmas yall,from texas,87 deluxe.

[84 silverado]

OK, first really dumb question is do you have plenty of coolant? If your low you may not have enough water circulation to go through the heater core. Next would be to check for an in-line heater control valve. This would be under the hood in one of your heater lines(hopefully they ARE hooked up) If you have one, check to see that it opens when the heater is turned to warm. If you don't have one.... well, nevermind. One way to see if you have water going to the heater box is to let the truck warm up good(thermostat opens) and see if your heater hoses are getting warm all the way to the firewall. If not you have no circulation. That's bad........ If you do have warm hoses, odds are you have a problem in the temp door under the dash. This may be vacumm or cable controlled on your truck. If this temp door doesn't open the heat never gets to your blower motor and you'll never get heat to the ducting. let me know what you find on it and maybe I can point you the right way, Bill

[j in la]

it could be a few things, obviously.i have once seen a waterpump with corroded ompellers do this.it wouldnt overheat but the water wouldnt circulate.also make sure there isnt a shutoff valve on the heater hose, that is pretty common.    

[87 texas deluxe]

I was told that maybe the hose coming out from my block could be clogged. Has any one done this before and if so, do I need to drain some of the radiator's antifreeze? Please reply .s. I'm going to check all water hoses.

[84 silverado]

I assume your truck is a V8 truck. If so, you'll have one hose coming from the front of the intake on the passenger side going to the firewall. This will be the feed hose for your heater. The other hose that returns from the firewall back to the radiator is.... well a return line. You should have warm water flowing thru both these hoses or your not going to get any heat at all. I've never seen the block end get clogged but I suppose it could happen. One easy way to check it for a clog would be to remove the hose from the intake and blow air thru it. You'll get some resistance at first due to the coolant that is in the core and hoses. Once it's cleared out though you should be able to blow air straight thru with the radiator cap removed. Give that a shot and feel the hoses while it's running. That's the only easy way I can tell you without putting my hands on it. Sorry, but good luck, Bill

[87 texas deluxe]

I've checked both hoses, from the wall to the engine to the radiator and I found flow on all of them but yet I've not been able to get heat in my cab.
I've been told that the problem has to be in the componets.
anyways thanks for your sugeestions and sorry about late replies but I've run into so many problem you don't even what to hear it all.
I'll probably cover them in other boards.thanks and later yall.

[84 silverado]

yeah, sounds like the flow is OK. Now you have to see about the control head and door actuators. See if they're working. One easy way is to first find the temp control door. Make sure it works when you run the control back and forth. I'm not sure if your's will be vacumm controlled or not but I'm guessing not. Should be cable operated. Make sure it's got full swing becuase if not you'll never get heat in the truck. I dunno any other way to do it without being there to show you. Sorry, Bill

[87 texas deluxe]

man, if it wasn't for u I swear.
I've recived answer from you at least 4 times all rendering a heck of alot money saved.
thanks alot guy and thanks again.
I will now go on to the steps you mantioned and let you know how It does. Later friend.

[84 K10 Silverado]

I had a 79 K10 4x4 w/a heater hose coolant heater that would only warm up the cab enough to keep you from freezing to death.....:-) Once I threw that piece of crap away, the heater worked great! Replaced it with a lower radiator hose heater and was warm and happy from then on.

[psc]

I have a 77 C-20 and the heat selector has a problem within itself.  The lever bounces back on mine because the cable was sticking; which did not allow the heat to go to the vents.  I put a little WD-40 on the sob and it worked just fine.  Just a little rusty, I guess